Lawrence J. Felice

DETERMINATION OF CATECHOLAMINES IN RAT BRAIN PARTS BY REVERSE‐PHASE ION‐PAIR LIQUID CHROMATOGRAPHY

An improved method for the measurement of catecholamines in brain parts has been developed, based on reverse‐phase ion‐pair chromatography. The new method offers the advantages of high efficiency microparticulate liquid chromatography packings and the flexibility of ion‐pair chromatography. By this approach norepinephrine and dopamine (DA) have been measured in the hypothalamus and corpus striatum of the rat brain during various stages of development (15, 21, 30 days). Data are reported on the basis of the whole part and per weight of tissue. For the adult animals, the following concentrations (ng/g wet tissue) were observed for the hypothalamus: NE = 2261 ± 274, DA = 440 ± 103, and for the corpus striatum: DA = 11,888 ± 1840. The overall precision of the method was ±5.6% relative s.d. The absolute recovery was 60 ± 5% relative s.d. and was constant over the range of 1 ng to 1 μg of dopamine or norepinephrine per tissue sample. The relative retention behavior of 18 neurologically important catechol derivatives is reported for reverse‐phase chromatography with octyl sulfate as the stationary phase modifier.

A modification of the pisano method for vanilmandelic acid using high pressure liquid chromatography

A method for the measurement of urinary vanilmandelic acid (VMA) is described based on a modification of the colorimetric procedure of Pisano. VMA is oxidized to vanillin with subsequent measurement of the vanillin by high pressure liquid chromatography with electrochemical detection (LCEC). The technique has been successfully applied to a number of human and animal urine samples. Urinary VMA values obtained by the LCEC method are in good agreement with those determined by the method of Pisano. The new method is both more selective and more sensitive than the colorimetric procedure.

Detectors for Trace Organic Analysis by Liquid Chromatography: Principles and Applications

Although liquid column chromatography (LC) had been used as a means of chemical separation for many years prior to 1969, it was not accepted as a method useful for rapid, routine analysis, due to the relatively long times required to achieve resolution. Significant theoretical and technological advances have since been made in this field, and excellent separations can now be achieved within a few minutes using high-efficiency LC column packings. Liquid chromatography offers many advantages over gas-liquid chromatography (GLC) in that no restrictions are placed on the size, volatility, or thermal stability of the sample molecules. In addition, LC offers tremendous flexibility in the choice of mobile and stationary phases such that most sample components can be conveniently resolved using some appropriate combination of mobile and stationary phases.